It is well known that air pollution from cars and trucks on Southern California freeways -- a combination of soot, pavement dust and other toxic substances -- can cause respiratory disease, heart attacks, cancer and premature death.

Now, exposure to pollution particles roughly one-thousandth the width of a human hair has been linked to brain damage in mice, including signs associated with memory loss and Alzheimer’s disease, according to a USC study in the journal Environmental Health Perspectives.

In a statement, senior author Caleb Finch, an expert on the effects of inflammation and holder of USC's ARCO/William F. Kieschnick Chair in the Neurobiology of Aging, said “You can’t see them, but they are inhaled and have an effect on brain neurons that raises the possibility of long-term brain health consequences of freeway air.”

The study relied on a unique technology developed at USC for collecting particulates in a liquid suspension and recreating air laden with freeway particulate matter in the laboratory, which enabled scientists to conduct controlled experiments on cultured brain cells and live animals.

Exposure lasted a total of 150 hours, spread over 10 weeks, in three sessions per week lasting five hours each.

How can we protect the millions of people who live alongside freeways from this type of toxicity?

In an interview, lead author Todd Morgan, a research professor in gerontology at USC, said, “Our data would suggest that freeway pollution could have a profound effect on the development of neurons and brain health in children and young kids, especially those who attend schools built alongside freeways.”

The study was prompted by earlier research by a separate group in Mexico that noted significant differences in brain samples collected from children and young-adult accident victims in smog-laden Mexico City compared with those in Veracruz, which has cleaner air.

The brain tissue collected in Mexico City showed more extensive inflammation, oxidized DNA and other pathological markers of Alzheimer’s disease, Morgan said.

“As a society, we need to figure out ways to minimize the level of the very, very nasty particulates we are dumping into the air we breathe,” Morgan said. “It’s having terrible consequences.”